Police use of hypnosis -- reliable tool or huge risk?

The detective talks calmly to the tense young man sitting before him in the overstuffed armchair.

Leaning back, the man relaxes as the detective assures him that there is no danger of reliving the terror of his kidnapping, where abductors pushed a barrel of a gun against his temple and clicked the trigger twice. The hypnotic trance, says the detective, will only spur recollection of details blocked out by fear.

The detective's soft monotone continues, and the man's eyes slowly close as he watches the glass ball on the gold chain. The man relaxes. He seems oblivious to loud traffic noises outside the window.

The detective starts the ''time regression'' trip back to the day of the kidnapping. The man starts to recall, in minute detail, what happened that day. . . .

The case is still under investigation. But episodes like this one are an increasingly common part of American law enforcement. Courts starting to have second thoughts

But in law enforcement, where hypnosis has been growing in popularity for the past 20 years, courts are starting to have second thoughts. The US Supreme Court Oct. 4 upheld a California Supreme Court ruling made earlier this year that made California one of five states to ban the courtroom testimony of witnesses who have been hypnotized. Rulings like these could slow the growing popularity of investigative hypnosis, says Bernard Diamond, professor of clinical psychology at the University of California at Berkeley.

Law enforcement officials say hypnosis relaxes crime victims and witnesses enough to dissolve the mental blocks to remembering details that could help police investigation.

The reason for the recent crackdowns, say the courts: hypnosis is too easily abused to allow hypnotically induced testimony in a criminal trial. Instead of improving memory, hypnosis may only manipulate it.

Six states allow court testimony culled from investigative hypnosis sessions done under certain strict guidelines, and eight states have no restrictions at all. The other states have no law on the subject. Some key questions

In the current controversy over hypnosis are these key questions:

* What is the effect on those put into a trance?

* If hypnotism is allowed, who is qualified to perform it?

* Should guidelines be set for conducting the hypnosis sessions? If so, by whom?

* Who should be hypnotized in a criminal investigation? The victim? Witnesses? The defendant?

* Is it ethical to ask subjects to be hypnotized?

Patrick Brady, chief of the hypno-investigation unit of the Boston Police Department, says he doesn't even like to use the word ''hypnosis'' because it scares people by conjuring up visions of mental manipulation. He has tried to redefine the word, calling it ''a more focused kind of awareness.''

But Webster's New World Dictionary defines hypnotism as ''a sleep-like condition psychically induced, usually by another person, in which the subject is in a state of altered consciousness and responds, with certain limitations, to the suggestions of the hypnotist.''

The controversy is perhaps most heated on the question of what impact hypnotism has on its subjects. Does it simply dredge up forgotten details to the surface of memory? Or does it actually create memory (''confabulation'')? Induces a state of suggestibility

Both supporters and opponents admit that hypnotism induces a state of suggestibility. But the question is whether that makes the subject too vulnerable to either accidental or purposeful leading by the hypnotist.

Mr. Brady says there is no evidence that hypnosis increases the chances that individuals will confabulate.

''People give more details in hypnosis, but among the details are more inaccuracies,'' says Fred Frankel, professor of psychiatry at Harvard Medical School and president of the International Society of Hypnosis. ''(Under hypnosis) people have less resistance, fewer defenses and inhibitions, so they'll share things they're not sure of. . . . Police say (testimony) is more reliable because of hypnosis. I'm saying that it's less reliable because of hypnosis.''

''Even the most skilled cross-examiner can't tell whether it's real memory or confabulation,'' says Houston defense attorney Jack Zimmerman.

Most court rulings on hypnotism have been handed down in the last two years, but investigative hypnosis has been common since the mid-1960s, when it was used in the highly publicized Boston Strangler case. Under hypnosis, one of the victims who survived the attacks described Albert De Salvo, who eventually confessed to the murders. The problem of adequate training

William Hoffman, director of the American Society of Clinical Hypnosis, insists that only trained medical personnel should attempt such a risky undertaking. A crime witness or victim, he says, could be traumatized by a mental journey back to the incident.

According to Frankel, at least a thousand police officers have had brief hypnosis training sessions with law enforcement hypnotist Martin Reiser of the Los Angeles Police Department. With such common use in local investigations, Frankel says, hypnotism is likely to be abused, and court cases dealing with the abuse are just now wending their way up through state courts.

The controversy often involves a power struggle between police and psychiatrists over who should perform the hypnosis. Police sometimes turn to hypnosis to solve brutal murder cases where all investigative leads have run dry. ''If you have nowhere else to go, why not use a hypnotist?'' Brady asks.

But critics of investigative hypnosis say the police usually know the circumstances of a case, and so are more likely to ''lead'' a subject in hypnotic questioning. Health professionals suggest that the police are more concerned with squeezing information out of a witness than they are with the person's mental safety.

But police cite a number of cases where they say hypnosis has yielded results. Perhaps the most famous use of investigative hypnosis was in the kidnapping of a schoolbus with 26 children and driver in Chowchilla, Calif. Apparently as a result of having been hypnotized, a witness was able to recall the full license number of a van driven by the kidnappers. Police hypnotist defends practice

Mr. Reiser cites Los Angeles Police Department statistics: through hypnosis, additional information has been gleaned in 75 percent of the cases since he started hypnosis for the LAPD in 1975. He claims 16 percent of the cases were solved primarily because of hypnosis.

Martin Orne, a University of Pennsylvania professor of psychiatry, advocates the use of hypnosis in criminal investigations only under strict guidelines. He has drafted guidelines which include videotaping of each hypnosis session and requiring a mental health professional to perform the hypnosis.

Hypnotism supporters such as Los Angeles District Attorney John Van de Kamp, say the courts should decide whether to allow hypnosis testimony on a case-by-case basis. In future California cases, he says, hypnosis will probably only be used to develop leads. ''There'll be virtually no hypnosis of victims.''